Tin compounds in sediments of Lake Maryut, Egypt

Concentrations of inorganic, methyl- and butyltin compounds were quantified by a hydride derivatization/atomic absorption technique for eleven short sediment cores sampled from Lake Maryut, Alexandria, Egypt. All samples contained inorganic Sn concentrations ranging from 1875 to 8190 ng g(-1) dw, the highest levels occurring in the eastern portion of the lake. Methyltin concentrations were also highest in the eastern lake, decreasing considerably in the western lake. Mono- and dimethyltins were found at all sites, the former species being the highest in concentration. Trimethyltin was much lower than either, and was absent from four out of 11 sites. An opposite trend was observed for the butyltin species, their concentration being highest in the west lake, decreasing eastward. Mono- and dibutyltin were almost equal in concentration. Although tributyltin was absent from one site in the lake, it was much higher in concentration than the two other species, particularly in the western lake. In general, methyl- and butyltin concentrations decreased with depth in the cores. Methyltin compounds appear to form within the lake mainly by methylation of inorganic Sn, and butyltin compounds are derived from anthropogenic sources. No significant correlations were found between organic C and concentrations of methyltin species. A significant negative correlation was found between total butyltin concentrations and organic C in surficial sediments.